Refrigerated display case

ABSTRACT

A refrigerated display case having a display space therein is provided with an access opening in the front of the case and an air curtain composed of a plurality of adjacent layers of air is directed across the access opening with the innermost layer of air adjacent the display space being at a higher temperature than an adjacent layer of air. Some of the air from the air curtain may be directed inwardly for circulation within the display space if desired. Refrigerated means are provided for refrigerating the air forming at least some of the layers of air forming the air curtain and the air forming the innermost layer of the air curtain may flow through a passage which by-passes the refrigeration means. The display space also may be provided with a rear access opening and duct means for circulation of the air forming the air curtain may have portions extending vertically upward at opposite sides of the rear access opening.

.United States Patent 1 Ma'cMaster et al.

[111 3,827,254 Aug. 6, 1974 REFRIGERATED DISPLAY CASE [75] Inventors: Malcolm D. MacMaster, Yardley;

Herbert R. Morris, Morrisville, both of Pa.

[73] Assignee: Emhart Corporation, Bloomfield,

v Conn. [22] Filed: May 4, 1973 21 Appl. No: 357,331

[52] US. Cl 62/256, 62/89, 62/458 [51] Int. Cl. A47f 3/04 [58] Field of Search 62/255, 256

[56] References Cited UNITED STATES PATENTS 2,984,085 5/1961 Rainwater 62/256 2,993,349 7/196] Detwiler 62/256 3,756,038 9/1973 MaCMaster 62/256 Primary Examiner-William J. Wye Attorney, Agent, or FirmSperry and Albert 5 7 ABSTRACT A refrigerated display case having a display space therein is provided with an access opening in the front of the case and an air curtain composed of a plurality of adjacent layers of air is directed across the access opening with the innermost layer of air adjacent the display space being at a higher temperature than an adjacent layer of air. Some of the air from the air curtain may be directed inwardly for circulation within the display space if desired. Refrigerated means are provided for refrigerating the air forming at least some 0f the layers of air forming the air curtain and the air forming the innermost layer of the air curtain may flow through a passage which by-passes the refrigeration means. The display space also may be provided with a rear access opening and duct means for circulation of the air forming the air curtain may have portions extending vertically upward at opposite sides of the rear access opening.

16 Claims, 4 Drawing Figures PATENTEUMIB 6 14 3.827.254

I SHEET 2 BF 3 FIG 3 REFRIGERATED DISPLAY CASE FIELD OF INVENTION It is common practice today to provide refrigerated display cases with an access opening in the front thereof and to establish an air curtain composed of one or more layers of air directed across the access opening to oppose the entry of ambient air into the display space. In some instances such cases are also provided with a rear access opening which is normally closed by sliding doors or the like. Typical display cases of this type are shown in U.S. Pat. Nos. 2,822,672; 3,182,466; 3,289,432; 3,287,929; 3,675,440.

The air forming the air curtain in such display cases is generally refrigerated and is often composed of several layers of air having different temperatures. In order to maintain the display space at a desired temperature, say about 30F, it is necessary to overcome heat losses to the ambient atmosphere through the air curtain and walls of the fixture and for this reason the air forming the innermost layer of the air curtain has heretofore been cooled to a temperature substantially lower than that desired in the display space, say to about 20F or lower. However, since the air curtain travels across the access opening at a relatively high speed and since the air temperature is reduced whereby the pressure of the air within the display space is reduced below that of the ambient air in front of the case. As a result, the air curtain tends to be deflected or bowed inwardly toward the display space causing a part of the low temperature air forming the innermost layer of air to circulate within the display space. It is then found that a frost build-up and over-cooling or freezing of products on display frequently takes place. When there are shelves in the display space this problem is particularly troublesome in the space above the uppermost shelf and adjacent the cold air discharge opening where the refrigerated air has the lowest temperature and is traveling at the highest velocity.

It is also found that the temperature of the air in the air curtain tends to rise as it moves across the access opening and mingles with ambient air due to turbulence at the interface between the ambient air and air curtain. It is therefore difficult to maintain the various areas above or between the shelves and in a bin at the bottom of the display space at uniform or predetermined temperatures. Moreover, in practically all air curtain cases of the prior art, there is a tendency for substantial amounts of cold air to spill out of the front of the case adjacent the lower edge of the access opening with a resultant loss of refrigeration.

In accordance with the present invention, these difficulties and objections of the prior art are reduced or eliminated and constructions are provided wherein over-cooling of products in the display space is prevented, more uniform temperatures are maintained and the spillage of cold air from the case is reduced.

These advantages are preferably attained by providing display cases having an access opening at the front thereof with an air curtain traveling across the access opening and composed of multiple layers of air wherein the innermost air layer is refrigerated to a lesser extent than an adjacent outer layer of air in the air curtain. Over-cooling of the display space is thus prevented and a portion of the innermost layer of air in the air curtain may safely be circulated within the display space to maintain the products at the desired temperature. In this way also the pressure of the air within the display space is increased sufficiently to reduce inward deflection of the air curtain. At the same time the adjacent outer layer of colder air in the air curtain reduces or prevents the innermost layer from increasing significantly in temperature as it travels across the access opening whereby more uniform or predetermined temperatures may be maintained at various points throughout the display space.

The construction further may be provided with an opening at the rear of the display space near the lower portion thereof through which a part of the air being circulated may be withdrawn so that spillage of cold air over the lower edge of the access opening at the front of the case is reduced.

THE DRAWINGS FIG. 1 is a vertical sectional view through a typical form of display case embodying the present invention taken on line lll of FIG. 2;

FIG. 2 is a horizontal sectional view of the construction shown in FIG. 1 taken on the line 22 thereof;

FIG. 3 is a vertical sectional view of the construction shown in FIG. 1 taken on the line 3-3 of FIG. 2; and

FIG. 4 is a perspective view of the rear side of the dis play space of the equipment illustrated in FIG. 1 illus' trating a detail of the construction.

PREFERRED EMBODIMENT In that form of the invention chosen for purposes of illustration in the drawings, the display case has an insulated base 2, an insulated rear wall 4 and an insulated top 6. The display space 8 within the case has an access opening 10 at the front thereof through which customers may reach to remove articles from the shelves 12 in the display space or from the bin. 14 in the lower portion thereof. The display space may also be provided with one or more rear access openings 16 which are normally closed by sliding doors 18 or the like.

Means are provided for establishing an air curtain moving across the front access opening 10 and for this purpose a return air inlet means 20 is located adjacent the lower edge of the access opening and a plurality of generally parallel air discharge outlets are located adjacent the upper edge of the front access opening. As shown, the innermost air discharge outlet closest to the display space 8 is indicated at 22, an adjacent or central air discharge outlet is indicated at 24 and an outer air discharge outlet is shown at 26. Air from the return air inlet means 20 is passed through duct means to the air discharge outlets 22, 24, and 26. The duct means extends from inlet 20 beneath the bottom 28 of the bin 14 of the display space 8 to a lower plenum chamber 30 located below the rear access openings 16. Columns 32 at opposite sides of the rear access openings 16 serve as vertically extending portions of the duct means and communicate with an upper plenum chamber 34 located above the rear access opening. A plurality of blowers 36 in the upper plenum chamber 34 serve to circulate air through the duct means from the air inlet 20 to the three air discharge outlets 22, 24 and 26 from which the air is directed downwardly across the front access opening for return to the air inlet 20.

Refrigerating means are located in the duct means to refrigerate the air thus circulated and are preferably in the form of an evaporator 40 located in the upper plenum chamber 34.

The evaporator is provided with a plate 42 adjacent the bottom thereof which is spaced from a panel 44 at the top of the display space 8 to form a passage 46 located below the evaporator 40 and extending from the rear of the plenum chamber 34 to the innermost air discharge outlet 22 so as to by-pass the evaporator 40. In a similar way a plate 48 is located above the evaporator 40 and is spaced from the top 6 of the case so as to form a passage 50 which extends from the rear of the plenum cahmber 34 to the front air discharge outlet 26 in a manner to by-pass the evaporator 40. The plates 42 and 48 serve to provide a central passage 52 in which the evaporator 40 is located and through which air from the rear of the plenum chamber 34 is passed to the central air discharge outlet 24. While only a single blower 36 is illustrated in the drawings a plurality of blowers will normally be provided and if desired, a separate blower may be provided for moving air from the plenum chamber through each of the by-pass passages 46 and 50 in the desired volume and at a desired velocity.

In this way an air curtain composed of three layers of air, indicated at 54, 56, and 58, is established and is directed across the front access opening to the return air inlet means for recirculation. The air flowing through lower passage 46 to the innermost air dis charge outlet 22 and forming the inner layer 54 of the air curtain is cooled by heat exchange with the evaporator through plate 42 and in a typical operation may have a temperature of about F to F. The air flowing through the upper passage 50 above the evaporator to the outer air discharge outlet 26 and forming the outer layer 58 of the air curtain will be cooled in a similar way and may have a temperature of about 40F to F. However, the air flowing through and in direct contact with the evaporator 40 through the central passage to the central air discharge outlet 24 serves to form the central layer 56 of the air curtain and will be cooled to a temperature below that of the air layers 54 and 58 and may be at a temperature of only about 20F.

In most installations an outer guard layer of ambient air 60 is directed downward on the outer side of the air curtain to reduce intermingling of ambient air with the air curtain and for this purpose a blower 62 is arranged to discharge ambient air through a discharge nozzle 64 adjacent the outer air discharge outlet 26 at the upper edge of the access opening.

The air curtain thus established, effectively opposes the entry of ambient air into the display space through the front access opening 10. At the same time, the colder central air layer 56 serves as a reservoir of cold air which prevents significant rise in temperature of the innermost layer of air 54 as it moves downward toward the return air inlet means 20.

The provision of an air curtain which has the innermost layer thereof maintained at a temperature approximating that at which the articles on display are to be maintained, renders it possible to safely circulate a portion of the air from the air curtain inward through the display space and about the articles on the shelves and bin therein. For this purpose a deflector 66 may be located adjacent the front edge of the shelf 12 in position to be contacted by the innermost layer 54 of the air curtain to direct such air into the space above the shelf and about the articles thereon. The rear edges of the shelves 12 in the display space are preferably provided with extensions 68 which extend rearwardly between the columns 32 which form the vertically extending portions of the duct means but are spaced from the doors 18 in the rear access openings 16 so as to provide air channels 70 through which air may flow downward at the rear of the shelves. The circulation of air thus provided assures the desired uniform cooling of all of the products on display and eliminates stagnant air pockets whereby all of the articles in the display space are maintained in a fresh, attractive and properly refrigerated condition.

The active circulation of air within the space above the shelves 12 also serves to increase the static pressure within such spaces sufficiently to oppose the atmospheric pressure of ambient air on the outer side of the air curtain whereby the tendency for the air curtain to be deflected inwardly is decreased. As a result, it is possible to maintain more nearly uniform or predetermined temperatures within the various portions of the display space. In fact, it is found that selected spacing of the rear edges of the shelves from the rear wall or doors 18 of the display space to provide controlled air channels 70 of predetermined width renders it possible to establish and maintain uniform temperatures above each shelf 12 and in the bin 14 of the case. In the alternative, it is possible to establish and maintain different temperatures in different areas of the display space as desired by varying the width of the air channels 70 at the rear of the shelves 12. This may also be accomplished by varying the volume and velocity of the air discharged through the innermost air discharge outlet 22 to form the inner layer 56 of the air curtain. Such variations may be effected by the use of a separate blower, change in the size of the passage 46 or the size of the discharge outlet 22 or in various other ways as desired. The construction thus lends itself to various different uses and types of operation to attain the optimum conditions for the preservation and display of meats, dairy products and other types of products requiring refrigeration.

Since the air forming an air curtain and approaching the return inlet means generally travels at a relatively high velocity and tends to entrain some ambient air therewith, air curtain display cases of the prior art are found to cause a portion of the refrigerated air to spill outward over the lower edge of the access opening into the aisle in front of the case. This condition is increased by the build up and turbulence of air entering the bin at the bottom of the display space and moving forward to the return air inlet. The resulting spillage of cold air from the case not only causes discomfort to customers but also represents a significant loss in refrigeration efficiency. In accordance with the present invention this difficulty is reduced or overcome and the desired temperature is more readily maintained inthe bin 14, by providing the rear wall 72 of the bin in the lower portion of the display space with a slot or opening 74 communicating with the lower plenum chamber 30 below the rear access opening 16 of the case. Since the lower plenum chamber is downstream, or on the inlet side of the blowers 36 by which the air forming the air curtain is circulated, air is drawn into the lower plenum chamber 30 through slot 74 from the bin 14 of the display space. The build up pressure in the bin and the turbulence of air therein is reduced in this way whereby the temperature in the bin is controlled and spillage of cold air over the lower edge of the access opening into the aisle in front of the case is reduced or eliminated.

The display case shown in the drawings and described above is particularly adapted for the preservation and display of meats, dairy products, and other articles which are best maintained at temperatures in the range of about 30F to 50F. However, many of the features of the present invention are adapted for use in refrigerated equipment employed for use at lower or higher temperatures and in constructions which do not have a rear access opening to the display space.

In view thereof, it should be understood that the particular embodiment of the invention disclosed herein is intended to be illustrative only and is not intended to limit the scope of the invention.

We claim:

1. A refrigerated display case having a display space therein with an access opening at the front thereof, means establishing an air curtain across the front of the access opening including a plurality of substantially parallel layers of air, and means for refrigerating the air making up at least a portion of said layers of air in said curtain, the innermost one of said layers of air adjacent said display space being maintained at a higher temperature than an outer layer of air adjacent thereto.

2. A refrigerated display case having a display space therein with an access opening at the front thereof, means for establishing an air curtain across the front of the access opening including adjacent parallel layers of air, a plurality of air discharge outlets located in parallel relation adjacent one edge of the access opening with one of said air discharge outlets being an inner discharge outlet positioned closer to said display space than another of said discharge outlets, return air inlet means adjacent the opposite edge of said access opening, duct means extending from said return air inlet means to said air discharge outlets, an evaporator located in said duct means for refrigerating air passing therethrough, and a blower for circulating air from said air inlet means through said duct means to said air discharge openings, said duct means including a by-pass passage located at one side of the evaporator and leading to said inner air discharge outlet.

3. A refrigerated display case as defined in claim 2 wherein means are provided for circulating air from the innermost layer of said air curtain inwardly through said display space.

4. A refrigerated display case as defined in claim 2 wherein there is a shelf within said display space, and means located near that edge of the shelf adjacent to the air curtain are formed to direct air inwardly from said air curtain into the space above said shelf.

5. A refrigerated display case as defined in claim 2 wherein at least a portion of said duct means is located at the rear of said display space and means are provided for circulating air from said air curtain rearwardly through said display space to said portion of said duct means.

6. A refrigerated display case as defined in claim 2 wherein there are three air discharge outlets one of which is centrally located between an inner discharge outlet and an outer discharge outlet, and said duct means includes a passage serving to lead air over said evaporator to said centrally located air discharge outlet and includes other passages which by-pass said evaporator and lead air to said inner and outer air discharge outlets.

7. A refrigerated display case as defined in claim 6 wherein said evaporator is located within a portion of said duct means above said display space and that passage leading to the inner air discharge outlet extends below the evaporator and that passage leading to the outer air discharge outlet extends above the evaporator.

8. A refrigerated display case having a display space therein with a front access opening in the front thereof and at least one rear access opening in the rear thereof, a door normally closing said rear access opening, means for establishing an air curtain across said front access opening including a plurality of adjacent parallel layers of air, parallel air discharge outlets located adjacent the upper edge of the front access opening and a return air inlet opening adjacent the lower edge of the front access opening, duct means extending from said return air inlet opening to said air discharge outlets and including a lower plenum chamber located below said rear access opening, an upper plenum chamber located above said rear across opening and vertically extending portions located on opposite sides of said rear access opening and communicating at their lower and upper ends respectively with said lower and upper plenum chambers, refrigerating means located in one of said plenum chambers, blowers for circulating air from said air inlet means through said duct means to said air discharge outlets to maintain said air curtain and means for directing a portion of the air from the innermost layer of said air curtain into said display space.

9. A refrigerated display case as defined in claim 8 wherein said refrigerating means includes an evaporator located in said upper plenum chamber and a passage which by-passes said evaporator extends from said upper plenum chamber to at least one of said air discharge openings.

10. A refrigerated display case as defined in claim 8 wherein a passage extends from said upper plenum chamber below said evaporator to that one of said air discharge outlets which is closest to said display space.

11. A refrigerated display space as defined in claim 8 wherein there is a shelf in said display space having means thereon adjacent the front edge thereof for directing air from the air curtain into the space above said shelf.

12. A refrigerated display case as defined in claim 1 1 wherein the rear edge of said shelf is spaced from the door in said rear access opening and cooperates therewith to provide a path for the flow of air downwardly at the rear of the display space.

13. A refrigerated display case as defined in claim 8 wherein said lower plenum chamber is provided with an opening through which air may flow from said display space into said lower plenum chamber.

14. A refrigerated display case as defined in claim 8 wherein there is a shelf in said display space and an opening is provided in said lower plenum chamber communicating with the space below said shelf for drawing off air from below the shelf to said lower plenum chamber for recirculation. through said duct means.

15. A refrigerated display case having a storage space therein with an access opening in the front thereof, means for establishing an air curtain directed across said access opening and embodying three adjacent par- 16. A refrigerated display case as defined in claim 15 anal layers of air wherein one of Said layers is disposed wherein the temperature of the air in said one layer of between the other two layers 9 .formmg Sald .cur' air is approximately 15F below the temperature of the tam, and means for refrigerating said one layer of an to a temperature below the temperature of those layers of air in the layers of air on the Opposite Sides thereofair on the opposite sides thereof. 

1. A refrigerated display case having a display space therein with an access opening at the front thereof, means establishing an air curtain across the front of the access opening including a plurality of substantially parallel layers of air, and means for refrigerating the air making up at least a portion of said layers of air in said curtain, the innermost one of said layers of air adjacent said display space being maintained at a higher temperature than an outer layer of air adjacent thereto.
 2. A refrigerated display case having a display space therein with an access opening at the front thereof, means for establishing an air curtain across the front of the access opening including adjacent parallel layers of air, a plurality of air discharge outlets located in parallel relation adjacent one edge of the access opening with one of said air discharge outlets being an inner discharge outlet positioned closer to said display space than another of said discharge outlets, return air inlet means adjacent the opposite edge of said access opening, duct means extending from said return air inlet means to said air discharge outlets, an evaporator located in said duct means for refrigerating air passing therethrough, and a blower for circulating air from said air inlet means through said duct means to said air discharge openings, said duct means including a by-pass passage located at one side of the evaporator and leading to said inner air discharge outlet.
 3. A refrigerated display case as defined in claim 2 wherein means are provided for circulating air from the innermost layer of said air curtain inwardly through said display space.
 4. A refrigerated display case as defined in claim 2 wherein there is a shelf within said display space, and means located near that edge of the shelf adjacent to the air curtain are formed to direct air inwardly from said air curtain into the space above said shelf.
 5. A refrigerated display case as defined in claim 2 wherein at least a portion of said duct means is located at the rear of said display space and means are provided for circulating air from said air curtain rearwardly through said display space to said portion of said duct means.
 6. A refrigerated display case as defined in claim 2 wherein there are three air discharge outlets one of which is centrally located between an inner discharge outlet and an outer discharge outlet, and said duct means includes a passage serving to lead air over said evaporator to said centrally located air discharge outlet and includes other passages which by-pass said evaporator and lead air to said inner and outer air discharge outlets.
 7. A refrigerated display case as defined in claim 6 wherein said evaporator is located within a portion of said duct means above said display space and that passage leading to the inner air discharge outlet extends below the evaporator and that passage leading to the outer air discharge outlet extends above the evaporator.
 8. A refrigerated display case having a display space therein with a front access opening in the front thereof and at least one rear access opening in the rear thereof, a door normally closing said rear access opening, means for establishing an air curtain across said front access opening including a plurality of adjacent parallel layers of air, parallel air discharge outlets located adjacent the upper edge of the front access opening and a return air inlet opening adjacent the lower edge of the front access opening, duct means extending from said return air inlet opening to said air discharge outlets and including a lower plenum chamber located below said rear access opening, an upper plenum chamber located above said rear across opening and vertically extending portions located on opposite sides of said rear access opening and communicating at theiR lower and upper ends respectively with said lower and upper plenum chambers, refrigerating means located in one of said plenum chambers, blowers for circulating air from said air inlet means through said duct means to said air discharge outlets to maintain said air curtain and means for directing a portion of the air from the innermost layer of said air curtain into said display space.
 9. A refrigerated display case as defined in claim 8 wherein said refrigerating means includes an evaporator located in said upper plenum chamber and a passage which by-passes said evaporator extends from said upper plenum chamber to at least one of said air discharge openings.
 10. A refrigerated display case as defined in claim 8 wherein a passage extends from said upper plenum chamber below said evaporator to that one of said air discharge outlets which is closest to said display space.
 11. A refrigerated display space as defined in claim 8 wherein there is a shelf in said display space having means thereon adjacent the front edge thereof for directing air from the air curtain into the space above said shelf.
 12. A refrigerated display case as defined in claim 11 wherein the rear edge of said shelf is spaced from the door in said rear access opening and cooperates therewith to provide a path for the flow of air downwardly at the rear of the display space.
 13. A refrigerated display case as defined in claim 8 wherein said lower plenum chamber is provided with an opening through which air may flow from said display space into said lower plenum chamber.
 14. A refrigerated display case as defined in claim 8 wherein there is a shelf in said display space and an opening is provided in said lower plenum chamber communicating with the space below said shelf for drawing off air from below the shelf to said lower plenum chamber for recirculation through said duct means.
 15. A refrigerated display case having a storage space therein with an access opening in the front thereof, means for establishing an air curtain directed across said access opening and embodying three adjacent parallel layers of air wherein one of said layers is disposed between the other two layers of air forming said air curtain, and means for refrigerating said one layer of air to a temperature below the temperature of those layers of air on the opposite sides thereof.
 16. A refrigerated display case as defined in claim 15 wherein the temperature of the air in said one layer of air is approximately 15*F below the temperature of the air in the layers of air on the opposite sides thereof. 